Magnetic iron product and method of making same.



hysteresis loss.

TRYGVE D. YENSEN, OF SWISSVALE, PENNSYLVANIA.

MAGNETIC IRON PRODUCT AND METHOD OF MAKING SAME.

N 0 Drawing.

To all whom it may concern:

Be it known that I, TRYevE D. YENSEN, a

citizen of the United States, residing at Swissvale, county of Allegheny, and State of Pennsylvania, have invented certain new and useful Improvements in Magnetic Iron Products and Methods of Making Same, of which the following is a specification. The present invention relates to iron products having unusual magnetic properties and to methods of making the same, and it seeks to obtain products of this nature which combine in a high de ee certain desirable qualities not found itherto in any product.

The metals resulting from the improved process of production possess an extraordinarily high degree of magnetic quality including remarkably high magnetic permeability and unusually low coercive force and (Magnetic permeability is a measure of the ease with which a substance can be magnetized to a certain degree and is expressed by the variable quantity,

B M fi where H is the magnetizing force-in gilberts per cn1.-required to produce the magnetic induction bin gausses-in the substance. Hysteresis loss is the energy lost on reversal of the magnetism due to molecular friction.) Coercive force H is the value of H necessary to demagnetize the iron after it has been previously magnetized.

The products may take the form of rolling mill or bloomery ingots or castings or further products worked therefrom into suitable form and treated in the manner described hereinafter, and may or may not contain alloying elements.

In carrying out my improved process, I make use of a low carbon iron from which impurities such as phosphorus, sulfur and manganese have been reduced to a low figure, preferably to 0.05 per cent. or less, taken in the aggregate, by Well known methods. Electrolytically refined iron may be used for this purpose, but this is not essential. After the iron is cleaned it may be placed in a suitable receptacle, for instance, a magnesia-lined crucible, which is introduced into a vacuum furnace where the iron is melted and further refined by subjecting it to the action of the vacuum, the process to Specification of Letters Patent.

Patented Sept. 3, 191%.

Application filed March 6, 1916. Serial 1\To.'82,340.

' be carried on in any suitable manner at such a high temperature, at such a'pressure, and for such a length of time (for example from a to 2 hours, at an absolute pressure of about 2 cm. of mercury or even less, and at a bath temperature of at least 1550 C.) that gases to a large extent will be eliminated from the bath, and furthermore, that the carbon content of the finished product will be reduced to not more than a few hundredths of one per cent. For the best results the final carbon content should not be more than 0.01 per cent. As the carbon is eliminated by oxidation by the iron oxid present in the 1I'0I].

(C FGOZCO Fe) it may be necessary in some cases in which the iron does not contain sufiicient oxid to supplement this by adding the required amount.

The heat for the operation in coma may be supplied by means of electrical energy or by any other means that can be applied in cacao without adding impurities to the iron. By using an alternating electric current, however, eddy currents are produced in the iron, having a very desirable stirring and mixing effect, and for this reason such a current is recommended.

After the elimination of the carbon and the gases, the metal is to be further deoxidized if necessary to such an extent that the oxygen content of the finished products -is 0.05 per cent. or preferably less. This deoxidation may be accomplished very satisfactorily by the addition of silicon or aluminum to the molten bath while in cacao.

The reason for keeping the aforesaid impurities below thefigures specified is that as the iron cools the-impurities are precipitated from the solution (either liquid or solid) and lodge between the iron crystals so as to obstruct the path of the magnetic flux from crystal to crystal. Furthermorethe impurities are not generally precipitated as such, but rather in the form of iron compounds such as Fe C, Fe P, FeS, etc., which have magnetic properties much inferior to those of pure iron. For example, in iron containing 0.10 per cent. carbon a precipitate containing 15* 0.10 or 1.50 per twelve hours or more).

netic qualities hereinbefore mentioned for low and medium flux densities. But should it be necessary or desirable to forge, roll, machine, or otherwise mechanically treat the iron, this may be done, and in such cases the previous annealing and slow cooling may be-omitted, but it is essential to follow this treatment by annealing the products (at 900 to 1200 (3.), followed by slow cooling (at approximately the rate above referred to) to give the iron the high magnetic quality sought. In practice the products have been cooled at the rate of 30 C. per hour from 900 to 1100 C. in mono or surrounded by an inert gas.

No mechanical operation that will put a permanent internal strain on the finished products is to be applied subsequent to the slow cooling.

By the hereindescribed process it is possible to obtain iron with permeabilities up to ten times, and with varying degrees of coercive force and hysteresis losses even as low as one-tenth, that of the best commercial grades of iron known at present. The magnetic properties of the iron products of the above-described process, therefore, "are widely different from those of the iron products heretofore known. As measured by the Burrows compensated double bar and oke method, or by the Ring method, the re ned and treated metal may, for instance, have a magnetic permeability, u, at ordinary temeratures, of at least 13,000 and as high as $0,000 at flux densities, B, between 5,000 and 10,000 gausses and a hysteresis energy loss for B ,=10,000 and 15,000 of less than 1,000 and 2,000 and as low as 250 and 575 ergs per cu. cm. of metal er magnetic cycle, respectively. The coercive force for B 15,000 is less than 0.36 and may be as low as 0.085 gilberts per cm.

Pure vacuum fused iron made-in accordance with my invention has a specific weight of 7.9 to 8.10 which is up to 1 per cent. higher than that of the purest commercial iron made by any prior methods.

For the attainment of products with higher electrical resistance than is obtainable with the pure iron products it is necessary to alloy the iron with some other material, for example, by adding from 2 to 5 per cent. of aluminumor silicon to the molten bath. I have found that the addition of such amounts of aluminum or silicon can e' added to the pure iron without lowerin e magnetic quality much, if any, below, the figures given in the preceding paragraph. The best results have been obtained with a silicon content of 3 to 4 per cent., as this gives the best combination of high permeability, low hysteresis loss, and high electrical resistance. However, if such additions are made, precautions must be taken not to introduce impurities into the iron beyond the amounts previously specified; and if such impurities are introduced, they must be eliminated. For instance, carbon may be eliminated as already shown by the reaction,

molten state and at a high temperature may be placed in a vacuum tank and the alloying material like silicon or aluminum added to 1t as needed to keep or maintain the metal in a sufiiciently liquid state by the lowering of its melting point to carry on the operation. as previously specified. The heat liberated by the addition of these alloying materials will also assist in maintaining the temperature of the metal. Thus in the circumstance outlined it may not be necessary to add any external heat to the iron while in vacuo.

For the attainment of products with rela-' tively high permeabilities at high flux densities, alloying element's'like silicon or aluminum should not be added to the iron to any large extent (except in so far as such elements may be used as deoxidizing agents) as it is well known that they tend to lower the saturation intensity of the iron.-Cobalt.is the only element known at present that raises the saturation intensity of pure iron.It may furthermore be necessary for the attainment of such product to forge, roll, or otherwise mechanically work the iron.

By this treatment, the-vacuum fused iron, as hereinbefore described, will have higher permeabilities at high flux densities than the best commercial grades of iron known at The permeability for B=20,000'

present. gausses, for instance, will be at least 100 and that for B=18,000 gausses 250-400.

If, in addition to the high permeabilities the following values: I"

(1) Permeability.

For B:!3,0O010,0O0- gausses, the permeability p.:13,000-70,000.

For B:15,000 gausses, the permeability p.=5,00018,000.

For B:18,000 gausses, the permeability L2250 100.

For B:20,000 gausses, the permeability p.::at least 100.

(2) Coercive force.

For B:15,000 gausses, the coercive force H :0.0850.36 gilberts per centimeter.

(3) Hysteresis loss.

For B:10,000 gausses, the hysteresis loss:2501,000 ergs per cubic centimeter per cycle.

For B:15,000 gausses, the hysteresis loss:5752,000 ergs per cubic centimeter per cycle.

Commercial grades of iron of a high degree of purity containing as low as 0.01 per cent. carbon are improved to a very large extent magnetically by remelting in vacuo.

One phase of the process has been described as including the melting of the iron in the vacuumfurnace. It will be understood, however, that the invention contemplates the use of molten metal rendered so by other means than the action of the vacuum furnace, in which circumstance the molten metal would be introduced into this furnace or a vacuum tank and there subjected to the stages of treatment described.

It is also to be understood that the specific apparatus, materials and process steps which have been described herein are intended to illustrate my invention and not to impose restrictions thereon, and that my invention comprises all such modifications and adaptations as fall within the scope of the appended claims.

It is to be understood that in the specification and appended claims the terni vacuum includes any degree of sub-atnibspheric pressure which will produce the efi'ects described above and that the term annealing covers heating and slow cooling as described hereinbefore.

Having thus described my invention What I claim as new and desire to secure by Letters Patent is:

1. The method of making a magnetic iron product which consists in melting a low carbon iron in mwuo and thereby refining the iron and imparting superior magnetic properties, substantially as described.

.2. The method of making a magnetic iron product which consists in subjecting a low carbon iron in vacuo to a high degree of heat to thereby melt and refine the iron, and treating the molten iron with a material capable of increasing its electrical resistance, substantially as described.

3.- The method of making an iron product having superior magnetic properties which consists in melting and refining a ferrous metal and subjecting the refined molten metal to the action of a vacuum to thereby degasify and further refine the metal, substantially as. described.

4. The method of making an iron product having superior magnetic properties which consists in melting and refining a ferrous metal and subjecting the refined molten metal to the action of a vacuum to thereby degasify and further refine the metal and treating the molten metal with a material capable of increasing the electrical resistance of the metal, substantially as described.

5. The method of making an iron product having superior magnetic properties which consists in melting andrefining a low carbon iron in vacuo, permitting the metal to solidify, and then mechanically working the solidified metal, substantially as described.

6. The method of making an iron product having superior magnetic properties which consists in melting and refining a low carbon iron in cacao, treating the molten iron with a material capable of increasing the electrical resistance thereof, permitting the metal to solidify, and then mechanically working the solidified metal, substantially as described.

7. The method of making an iron product having superior magnetic properties which consists in melting and refining a ferrous metal, subjecting the refined molten metal to the action of a vacuum to thereby degasify and further refine it, permitting the metal to solidify, and then mechanically working the solidified metal, substantially as described.

8. The method of making an iron product having superior magnetic properties which consists in melting and refining a ferrous metal, subjecting the refined metal while in a molten state to the action of avacuum to thereby degasify and further refine it, treating the molten metal with a material capable of increasing the electrical resistance thereof, permitting the metal to solidify, and then mechanically working the solidified metal, substantially as described.

. 9. The method of making an iron product having superior magnetic properties which consists in melting and refining a low carbon iron in vacuo, permitting the iron to solidify, mechanically working the solidified metal, and then annealing the metal, sub stantially as described.

10. The method of making an iron product having superior magnetic properties which consists in melting and refining a low carbon iron in vacuo, treating the molten iron with a material capable of increasing the electrical resistance thereof, then permitting the metal to solidify, mechanically working the metal, and then annealing, substantially as described.

11. The method of making an iron product having superior magnetic properties which consists in melting and refining a.

ferrous metal and subjecting the refined molten metal to the action of a vacuum to thereby degasify and further refine it, per-- mitting the metal to solidify, mechanically working the metal, and then annealing, substantially as described.

12. The method of making an iron product having superior magnetic properties which consists in melting and refining iron, and subjecting the molten metal to the action of a vacuum to thereby degasify and further refine it, treating the refined molten iron with a material capable of increasing the electrical resistance thereof, permitting the metal to solidify, mechanically Working the solidified metal, and then annealing, substantially as described.

which consists in subjecting a refined molten iron in which manganese, sulfur, and phosphorus have been reduced to 0.05 per cent. or less when taken in the aggregate, and carbon to 0.02 per cent. or less to the action of a vacuum, and treating the molten iron with a material capable of increasing the electrical resistance thereof, substantially as described.

15. The improved method of making an iron product having superior magnetic properties, which consists in subjecting a refined molten iron in which manganese, sulfur, and phosphorus have been reduced to 0.05 per cent. or less when taken in the aggregate, and carbon to 0.02 per cent. or less to the action of a vacuum, treating the molten iron with a deoxidizing agent to such extent that the product shall contain not over 0.05 per cent, oxygen, permitting the iron to solidify, and then mechanically working the solidified metal, substantially as described.

16. The method of making an iron product of superior magnetic properties which consists in subjecting a refined molten iron in which manganese, sulfur, and phosphorus have been reduced to not over 0.05 per cent. when taken in'the aggregate, and carbon to not over 0.02 per cent. to the action of a vacuum, and treating the molten iron with a material capable of increasing the electrical resistance thereof, permitting the metal to solidify, and mechanically working the solidified metal, substantially as described. i

17. The improved method of making an iron product having superior magnetic properties which consists in subjecting a refined molten iron in which manganese, sulfur and phosphorus have been reduced to not over 0.05 per cent. when taken in the aggregate, and carbon to not over 0.02 per cent. to the action of a vacuum, treating the molten iron with a deoxidizing agent to such extent that the product shall contain not over 0.05 per cent. oxygen, permitting the iron to solidify, mechanically working the solidified metal, and then annealing,

substantially as described.

18. The method of making an iron product of superior magnetic properties which consists in subjecting a refined molteniron in which manganese, sulfur, and phosphorous have been reduced to not over 0.05 per cent. when taken in the aggregate, and carbon to not over 0.02 per cent. to the action of a vacuum, and treating the molten iron with a material capable of increasing the electrical resistance thereof, permitting the metal to solidify, mechanically Working the solidified metal, and then annealing, substantially as described.

19. The method of making a magnetic iron product having superior magnetic properties which consists in melting a low carbon iron in vacuo and thereby refining the iron and then slowly cooling the product, substantially as described.

20. A magnetic metallic body, crystalline in structure, containing at least per cent.

iron and having intercrystalline impurity forming elements aggregating less than 0.15 per cent. and characterized by a magnetic permeability of 13,000-70,000 at a flux density between 5,000 and 10,000 gauss'es; substantially as described.

21. A magnetic metallic body, crystalline in structure, containing at least 90 percent. iron and having intercrystalline impurity forming elements aggregating less than 0.15 per cent. and characterized by a hysteresis energy 10,000 and 15,000 gausses of 250-1000 and 575-2000 ergs per cubic centimeter of metal per magnetic cycle respectively, substantially as described.

22. A magnetic metallic body, crystalline in structure, containing at least 90 per cent. iron and having intercrystalline impurity forming elements aggregating less than 0.15 per cent. and characterized by a coercive loss for maximum inductions of mamas force for a maximum induction of 15000 gausses of 0.0850.350 gilberts per centimeter; substantially as described.

A magnetic metallic body, crystalline in structure, containing at least 99.80 per cent. iron, having intercrystalline impurity forming elements aggregating not over 0.15 per cent. having specific weight of at least 7.0 and having a magnetic pern'ieability of 13,000 to 70,000 at a flux density of between 5,000 and 10,000 gausses; substantially as described. I

24. A magnetic metallic body, crystalline in structure, containing at least 90 per cent. iron, the remainder being chiefly silicon or aluminum, and having intercrystalline impurity forming elements aggregating less than 0.15 per cent, and characterized by a magnetic permeability of 13,00070,000 at a flux density between 5,000 and 10,000 gausses; substantially as described.

25. A magnetic metallic body, crystalline in structure, containing at least 90 per cent.

iron, the remainder being chiefly silicon or aluminum, and having intercrystalline impurity forming elements aggregating less than 0.15 per cent. and characterized by a hysteresis energy loss for maximum inductions of 10,000 and 15,000 gausses of 250 1000 and 5752000 ergs per cubic centimeter of metal per magnetic cycle respectively; substantially as described.

26. A magnetic metallic body, crystalline in structure, containing at least 90 per cent. iron, the remainder being chiefly silicon or aluminum, and having intercrystalline im-' purity forming elements aggregating less than 0.15 per cent. and characterized by a coercive force for a maximum induction of 15,000 gausses of 0.0850.350 gilberts per centimeter; substantially as described.

TRYGVE D. YENSEN.

Witnesses:

LILLIAN R. CROMWELL, MILTON T. MILLER. 

